The matrix layer 20 preferably is expanded, porous polytetrafluoroethylene, the wafers 38 are silicon, gallium arsenide or ceramic, with or without circuitry, the coating or impregnating dielectric polymer is a thermosetting polymer such as a cyanate ester, Benzocyclobutene (BCB) or a thermoplastic fluoropolymer or a preimidized polyimide.